Electrochromism of Methylviologen (Paraquat)

The herbicide paraquat, N, N’-dimethyl-4,4‘-bipyridiunium dication (N,N’-methyl viologen), is electrochromic. Experiments are described that investigate its redox chemistry (cyclic voltammetry), its optical properties (photometry and UV/Vis spectrophotometry), and its potential as a system for electrical “photoswitching” and as an accumulator for rechargeable devices. This set of teaching laboratory experiments closely reflects true procedures in commercial research and development endeavors, because the same system is probed with several quite different, but complementary, analytical methods.